A DC arc furnace electrically conductive hearth construction is disclosed by the Stenkvist et al. U.S. Pat. No. 4,324,943, the hearth construction including a brick wear lining through which metal electrical conductors extended from top to bottom of the lining, the wear lining resting on an electrically conductive construction through which DC arc current is carried via the wear lining conductors to a furnace melt directly supported on the wear lining, providing power for an arc formed with the melt and an arcing electrode positioned above the melt in the furnace.
The metal conductors extending through the wear lining brickwork must have their upper ends in contact with the melt and consequently at least the upper portions of the conductors become molten and in effect part of the melt carried by the wear lining. The conductors become molten only throughout their upper portions but their molten portions may extend a substantial distance downwardly from the top of the brickwork wear lining.
The bricks of the brickwork may be the usual dolomite or magnesite bricks known to have satisfactorily long service lives in more conventional hearth constructions but in the case of the conductive brick wear lining of the patent unusual brick wear has been experienced. The present inventor has analyzed this problem as follows:
The conductors' molten portions carry the arcing current to the melt and thus to the arc and although the current is distributed throughout the various wear bottom conductors the current carried by the molten portions of each conductor is substantial. This results in electromagnetic effects causing a circulation of the molten metal of the conductors in the bricks of the wear bottom brickwork, resulting in melt flows which erode away the bricks contacted by the melt flows.